From: Jens Axboe <qemu@kernel.dk>
To: qemu-devel@nongnu.org
Cc: aarcange@redhat.com, Gerd Hoffmann <kraxel@redhat.com>,
kvm-devel <kvm@vger.kernel.org>
Subject: Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool
Date: Fri, 12 Dec 2008 09:23:10 +0100 [thread overview]
Message-ID: <20081212082309.GI23742@kernel.dk> (raw)
In-Reply-To: <20081211181116.GE6809@random.random>
On Thu, Dec 11 2008, Andrea Arcangeli wrote:
> On Thu, Dec 11, 2008 at 06:20:09PM +0100, Gerd Hoffmann wrote:
> > Andrea Arcangeli wrote:
> > > On Thu, Dec 11, 2008 at 05:11:08PM +0100, Gerd Hoffmann wrote:
> > >> Yes. But kernel aio requires O_DIRECT, so aio users are affected
> > >> nevertheless.
> > >
> > > Are you sure? It surely wasn't the case...
> >
> > Tons of docs say so, but might be they are wrong, I didn't check.
>
> I guess those tons of docs are just wrong then ;). I see no mention of
> O_DIRECT in `man io_submit` at least... I seem to recall initially aio
> only worked without O_DIRECT... ;). It's quite the opposite, O_DIRECT
> works best with kernel aio, not the other way around. O_DIRECT
> read/writes look very much like non-O_DIRECT seeking reads. For
> seeking sync-reads kernel aio pays off as well as with O_DIRECT.
aio is only async with O_DIRECT, with buffered IO it's sync.
--
Jens Axboe
next prev parent reply other threads:[~2008-12-12 8:23 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-05 21:21 [Qemu-devel] [RFC] Replace posix-aio with custom thread pool Anthony Liguori
2008-12-06 9:03 ` Blue Swirl
2008-12-06 18:26 ` Jamie Lokier
2008-12-08 18:23 ` Anthony Liguori
2008-12-09 15:51 ` Gerd Hoffmann
2008-12-09 16:01 ` Anthony Liguori
2008-12-10 16:44 ` Andrea Arcangeli
2008-12-10 17:21 ` Anthony Liguori
2008-12-10 17:29 ` Gerd Hoffmann
2008-12-10 18:50 ` Anthony Liguori
2008-12-10 19:08 ` Andrea Arcangeli
2008-12-11 13:12 ` Andrea Arcangeli
2008-12-11 15:24 ` Gerd Hoffmann
2008-12-11 15:53 ` Andrea Arcangeli
2008-12-11 16:11 ` Gerd Hoffmann
2008-12-11 16:49 ` Andrea Arcangeli
2008-12-11 17:20 ` Gerd Hoffmann
2008-12-11 18:11 ` Andrea Arcangeli
2008-12-11 20:38 ` Gerd Hoffmann
2008-12-11 20:40 ` Anthony Liguori
2008-12-12 8:23 ` Jens Axboe [this message]
2008-12-12 11:51 ` Andrea Arcangeli
2008-12-12 11:54 ` Jens Axboe
2008-12-12 14:13 ` Andrea Arcangeli
2008-12-12 14:24 ` Anthony Liguori
2008-12-12 16:33 ` Chris Wright
2008-12-12 16:51 ` Anthony Liguori
2008-12-12 16:52 ` Chris Wright
2008-12-11 21:32 ` Christoph Hellwig
2008-12-12 0:27 ` Andrea Arcangeli
2008-12-11 21:30 ` Christoph Hellwig
2008-12-11 16:41 ` Anthony Liguori
2008-12-12 14:24 ` Andrea Arcangeli
2008-12-12 14:35 ` Anthony Liguori
2008-12-12 15:44 ` Andrea Arcangeli
2008-12-12 16:49 ` Anthony Liguori
2008-12-12 17:09 ` Andrea Arcangeli
2008-12-12 17:25 ` Anthony Liguori
2008-12-12 17:52 ` Andrea Arcangeli
2008-12-12 18:17 ` Anthony Liguori
2008-12-12 18:26 ` Andrea Arcangeli
2008-12-12 20:12 ` Gerd Hoffmann
2008-12-12 20:17 ` Anthony Liguori
2008-12-12 20:35 ` Gerd Hoffmann
2008-12-09 17:16 ` Avi Kivity
2008-12-17 14:44 ` Ian Jackson
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